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Acta polytechnica HungaricaVolume 11, Issue No. 5 (2014.)


  • Béla Palásti-Kovács ,
    Sándor Sipos ,
    Szabolcs Bíró :

    Abstract: In these days, the key elements for the reliability and the safe operation of technical devices are the following: surface of the tools, the surface quality and the roughness of the connecting elements. The present work is going to introduce the idea that different machining methods that create microgeometries that are very much different from each other and of diverse roughness parameter proportions. It will be shown that the wear and the change of the tool edge(s) ‒ resulting from the deterioration process of the tools, used during production ‒ cause significant arithmetical, average and form deviations. The uncertainties of the roughness measuring technique, arising during the evaluation of the real and filtered surface profiles, will be shown via samples.

    Keywords: machined surface; microgeometry; roughness; wear process

  • Abstract: Our work focuses on studying gait symmetry with the use of bilateral angle-angle diagrams. The geometric characteristics of angle-angle diagrams can be used to characterize gait, as well as, identify and quantify the associated gait asymmetry. The angle-angle diagrams were created for ten patients with leg length inequality (LLI), to quantify gait symmetry before and after an application of the heel lift. In order to quantify the symmetry of human walking, we have invented and used the characteristics of an angle-angle diagram, which represent the evolution of the two joint angles, i.e. left and right knee angles or left and right hip angles. The novel methods are based on the area of the convex hull of the hip-hip diagram or knee-knee diagram, and can be used as an additional method for the determination of gait symmetry of the bipedal walking of human subjects or robots. Our method is not limited to gait studies, it can also be used to study arm swing symmetry.

    Keywords: human walking; bipedal walking; convex hull; angle-angle diagram; length inequality

  • Gábor Kövesdán ,
    Márk Asztalos ,
    László Lengyel :
    Architectural Design Patterns for Language Parsers39-57en [566.84 kB - PDF]EPA-02461-00051-0030

    Abstract: Processing the textual scripts of computer languages is an important field in software development, which has been growing in popularity, recently. It is applied both for general-purpose programming languages and for domain-specific languages. There is a wide range of typical algorithms and patterns that are used to syntactically parse formal languages, each having specific characteristics and implying different software architectures. If we develop parsers at a higher abstraction level, it simplifies the problem domain and facilitates developing more robust software quicker, but there are always some tradeoffs to consider. The main guideline of this paper is abstraction: how to increase it in different patterns, how it helps parser development and what kind of tradeoffs are implied. The presented architectural design patterns are organized in a pattern catalog ordered by their abstraction level. This catalog is intended to assist developers in the industry in designing efficient parser software.

    Keywords: modeling; model-processing; formal languages; parsers; design patterns; architectural patterns

  • Velibor Karanović ,
    Mitar Jocanović ,
    Vukica Jovanović :

    Abstract: The design of modern robotic devices faces numerous requirements and limitations which are related to optimization and robustness. Consequently, these stringent requirements have caused improvements in many engineering areas and lead to development of new optimization methods which better handle new complex products designed for application in industrial robots. One of the newly developed methods used in industrial robotics is the concept of a self-contained power device, an Electro-Hydrostatic Actuator (EHA). EHA devices were designed with a central idea, to avoid the possible drawbacks which were present in other types of actuators that are currently used in robotic systems. This paper is a review of the development phases of an EHA device for robotic applications. An overview of the advantages and disadvantages related to current EHA designs are presented, and finally possible ideas for future developments are suggested.

    Keywords: electro-hydrostatic actuator; hydraulics; robotics

  • New Method for Evaluating the Visibility of Coronary Stents81-94en [752.35 kB - PDF]EPA-02461-00051-0050

    Abstract: In invasive radiology, X-ray imaging is used in both tracking the delivery system and assisting in correct positioning of stents. Until now there has been no objective and quantitative scale of X-ray visibility which is also known as radiopacity. There is a clear need from the part of interventional cardiologists for a quantitative in vitro evaluation method with which X-ray visibility can be graded repeatably, objectively, in a validated form across a wide range of fields. Therefore the development of the presented quantitative evaluation approach was decided in order to unambiguously classify the radiopacity of given cardiovascular implants under given in vitro imaging conditions. In this work the relative X-ray visibility index (XVR), which expresses the visibility of the stent compared to the background and the method for determining the value of this index, is introduced. The XVR index is related to a simple quantification method based on image analysis of X-ray images of stents. Nevertheless, this stent radiopacity quantification method can also be used in a wide range of clinical contexts.

    Keywords: stent; visibility; radiopacity; X-ray microscopy; image analysis

  • Görkem Kökkülünk ,
    Adnan Parlak ,
    Eyup Bagci ,
    Zafer Aydin :

    Abstract: In this study, optimal engine performance and pollutant emission conditions are investigated by using Taguchi Design Methods. Orthogonal arrays of Taguchi, the signal-to-noise (S/N) ratio and the analysis of variance (ANOVA) were employed to find the optimal levels and to analyze the effect of the operation conditions on performance and emission values. The parameters and their levels are engine speeds at 1200, 1600, 2000 and 2400 rpm, steam ratios of 0, 10, 20 and 30% and EGR ratios of 0, 10, 20 and 30%. Confirmation tests with the optimal levels of engine parameters were carried out in order to illustrate the effectiveness of the Taguchi optimization method. While steam and EGR ratios are found effective on emission parameters, significance levels for these parameters have been found low for effective power and torque. It was thus shown that the Taguchi method is suitable to solve the problems of performance and emissions for diesel engines.

    Keywords: Taguchi Method; Diesel Engine; Pollutant Emissions; EGR; Steam

  • Ferenc Erdős ,
    Gábor Kallós :
    Benefit Evaluation Model for Gamified Add-Ons in Business Software109-124en [614.57 kB - PDF]EPA-02461-00051-0070

    Abstract: Return on IT investment analysis has become a fundamental task of the finance function at corporations, let it be large multinational organizations or small and medium businesses (SME). Besides the cost analysis, the benefit analysis is also an essential component of economic calculations and decisions. Due to complicated profit calculations and estimation methods, the benefit of IT investments is less easily forecast and hence less frequently calculated than their costs. This study focuses on a special innovative type of IT investments, the gamified extensions of business software. Gamification, which refers to the use of game design elements in a non-gaming context, can expect big development in the field of business applications in the near future. Gamification features of business software generally enhance user experience, enabling people to do otherwise boring tasks. In the following we attempt to propose a sophisticated benefit evaluation model based on the hedonic wage model (HWM) and technology acceptance model (TAM) for this special type of IT projects.

    Keywords: gamification; business software; benefit; IT investment

  • Rafik Salloum ,
    Bijan Moaveni ,
    Mohammad Reza Arvan :
    Robust PID Controller Design for a Real Electromechanical Actuator125-144en [1.04 MB - PDF]EPA-02461-00051-0080

    Abstract: Electromechanical actuators (EMA's) are of interest for applications that require easy control and high dynamics. In this paper, we design a robust PID controller for position control of a real electromechanical actuator. An EMA is modeled as a linear system with parametric uncertainty by using its experimental input-output data. PID controllers are designed by graphical findings of the regions of stability with pre-specified margins and bandwidth requirements and by applying the complex Kharitonov's theorem. This novel method enables designers to make the convenient trade-off between stability and performance by choosing the proper margins and bandwidth specifications. The EMA control system is passed to the Bialas' test, and validated on the basis of meeting a desired set of specifications. The effects of parameter variations on the system’s stability and performance are analyzed and the simulation and test results show that the EMA with the new controller, in addition to robustness to parametric uncertainties, has better performance compared to the original EMA control system. The simulation and test results prove the superiority of the performance of the new EMA over the original EMA control system pertaining to its robustness to parametric uncertainties.

    Keywords: electromechanical actuator (EMA); robust PID controller; Kharitonov theorem

  • Livija Cveticanin ,
    Gyula Mester ,
    Istvan Biro :
    Parameter Influence on the Harmonically Excited Duffing Oscillator145-160en [700.07 kB - PDF]EPA-02461-00051-0090

    Abstract: In this paper the influence of the initial conditions and the interaction of the parameters on the motion of the strong nonlinear Duffing oscillator are investigated. The initial conditions are arbitrary and need not be zero. An analytical procedure for solving the strong nonlinear differential equation with excitation term is developed. The obtained solutions give the physical explanation of the excited vibrations caused by the excitation force and non-zero initial conditions. The analytical results are compared with numerical results and show good agreement.

    Keywords: Duffing oscillator; harmonic excitation; non-zero initial conditions; jump effect

  • Vagif M. Mirsalimov ,
    Fuad F. Hasanov :

    Abstract: We consider a plane problem of fracture mechanics for an isotropic medium with a periodic system of circular holes filled with absolutely rigid inclusions soldered along the contour and weakened by rectilinear cracks with interfacial bonds at the end zones collinear to the abscissa and ordinate axes of unequal length under transverse shear. The problem on equilibrium of isotropic composite medium with cohesive cracks is reduced to the solution of the system of nonlinear singular integro-differential equations with Cauchy type kernel. The tangential forces at the end zones of the cracks are found from the solution of this system of equations. The crack propagation condition is stated with regard to ultimate stretching of the material bonds.

    Keywords: isotropic medium; periodic system of circular holes; cohesive forces; rigid inclusions; transverse shear; prefracture zone; cracks with interfacial bonds

  • Francisca Nonyelum Ogwueleka ,
    Sanjay Misra ,
    Toochukwu Chibueze Ogwueleka ,
    L. Fernandez-Sanz :

    Abstract: Road traffic accidents (RTA) are one of the major root causes of the unnatural loses of human beings all over the world. Although the rates of RTAs are decreasing in most developed countries, this is not the case in developing countries. The increase in the number of vehicles and inefficient drivers on the road, as well as to the poor conditions and maintenance of the roads, are responsible for this crisis in developing countries. In this paper, we produce a design of an Artificial Neural Network (ANN) model for the analysis and prediction of accident rates in a developing country. We apply the most recent (1998 to 2010) data to our model. In the design, the number of vehicles, accidents, and population were selected and used as model parameters. The sigmoid and linear functions were used as activation functions with the feed forward-back propagation algorithm. The performance evaluation of the model signified that the ANN model is better than other statistical methods in use.

    Keywords: Artificial neural network; road; accident; linear function; back propagation; vehicles

  • Abstract: This paper presents a study on predicting academically at-risk engineering students at the early stage of their education. For this purpose, some soft computing tools namely support vectors machines and artificial neural networks have been employed. The study population included all students enrolled in Pamukkale University, Faculty of Engineering at 2008-2009 and 2009-2010 academic years as freshmen. The data are retrieved from various institutions and questionnaires conducted on the students. Each input data point is of 38-dimension, which includes demographic and academic information about the students, while the output based on the first-year GPA of the students falls into either at-risk or not. The results of the study have shown that either support vector machine or artificial neural network methods can be used to predict first-year performance of a student in a priori manner. Thus, a proper course load and graduation schedule can be transcribed for the student to manage their graduation in a way that potential dropout risks are reduced. Moreover, an input sensitivity analysis has been conducted to determine the importance of each input used in the study.

    Keywords: at-risk students; least-square support vector classification; radial basis functions neural network; support vector classification

  • Alireza Namadmalan ,
    Javad Shokrollahi Moghani :

    Abstract: This paper presents a new tuningloop for three-phase current source parallel resonant inverters. The switching frequency is tuned by using a phase-locked loop (PLL) circuit based on a new Phase Detector (PD). In practice, the resonant capacitors and inductors have tolerances that cause different resonant frequency for each phase. This paper shows that a conventional PDcauseshigher voltage stress over switches and DC-link inductor. In the proposed tuning loop, the PLL tracks the average value of the resonant frequencies that reduces the voltage stress. In addition, there is no feedback from the loadcurrents to detect the phase error, which is another advantage of the new method. A laboratory prototype of a three-phase current source parallel resonant half-bridge inverter was built to verify the advantages of the proposed tuning system with operating frequency of 22 kHz.

    Keywords: resonant inverter tuning; three-phase current source parallel resonant inverters; phase-locked loop (PLL)